It is well known that calcium levels in myoplasm control muscular contractibility. Active transport of calcium into the sarcoplasmic reticulum plays a major role in regulating calcium levels in the myoplasm. The membrane bound enzyme Ca ions plus Mg ions -ATPase from sarcoplasmic reticulum of skeletal muscle is known to be the primary protein involved in the active transport of calcium. The proposed project will examine the role of Ca ions -selective ionophore (or carrier) in energy transduction from the hydrolysis of ATP by Ca ions plus Mg ions -ATPase to the calcium ion in sarcoplasmic reticulum. Our studies have shown that solubilized Ca ions plus Mg ions -ATPase (S-Ca ion -ATPase) or a fragment of Ca ions plus Mg ions -ATPase from sarcoplasmic reticulum increases lipid bilayer membrane conductance several hundred fold. The relative conductance change and the relative permeability elicited by this material show the following sequence: Ba ions greater than Ca ions greater than Sr ions greater than Mn ions greater than Zn ions, Na ion, K ion, Cs ion, Li ion, and Rb ion. The divalent cation interaction with the Ca ions plus Mg ions -ATPase and with Ca ions -pump. This evidence indicates that the Ca ions -ionophore may be an integral part of the Ca ions plus Mg ions -ATPase enzyme and may function as a Ca ions -carrier in the overall Ca ions -pump of sarcoplasmic reticulum. Our studies have shown physically and chemically that the catalytic function of Ca ions plus Mg ions -ATPase resides in 30 K fragment and that the Ca ions -ionophoric site resides in the 20 K fragment. Both 30 K and 20 K fragments are part of 55 K fragment which faces the myoplasm. The objectives of this project are: to purify the smallest fragment of Ca ions plus Mg ions -APTase with Ca ions -ionophoric properties; to determine the role of phosphorylated intermediate in Ca ions -transport and/or Ca ions -ionophore, to elucidate the energy transduction from ATP hydrolysis to the calcium ion using physical and biochemical methods and employing natural and synthetc bilayer membrane; and to determine the role of natural body fluid ions such as Mg ions, Na ion, and K ion on the Ca ions -ionophore and Ca ions -uptake. Magnetic resonance of the purified Ca ions -ionophore (Text Truncated - Exceeds Capacity)